1. Field of the Invention
The present invention relates to a lens moving mechanism for linearly moving a lens in an optical axis direction via a rotational lead screw.
2. Description of the Related Art
In a known lens moving mechanism using a lead screw, a lens frame which holds a lens is slidably attached to a guide shaft extending parallel with the optical axis so as not to rotate. The lens frame is provided with a screw-engagement portion which engages with the lead screw extending parallel with the guide shaft.
In this lens moving mechanism, a compression coil spring is provided to bias the lens frame in the optical axis direction in order to eliminate backlash between the lead screw and the lens frame. However, as the amount of compression of the compression coil spring varies in accordance with the movement of the lens frame, the load applied to a motor which drives the lead screw varies accordingly. Furthermore, as a space for accommodating the compression coil spring in the optical axis direction is necessary, it is difficult to miniaturize the lens moving mechanism.
In another type of lens moving mechanism, a screw-engagement body which engages with the lead screw is constructed separately from the lens frame. In this type of lens moving mechanism, another compression spring is necessary to absorb play between the screw-engagement body (screw-engagement follower) and the lens frame. Therefore, it is necessary to provide a space in which the compression spring is accommodated in the optical axis direction and a space in which a support shaft of the engagement follower is supported. Consequently, it is difficult to miniaturize the lens moving mechanism. There is continuous need for miniaturization of a camera in which such a lens moving mechanism is incorporated. However, conventional lens moving mechanisms cannot satisfy the need for further miniaturization of a camera.